The invention relates to an apparatus and method for the preparation of hot beverages by brewing a water-extractable particulate substance for preparing hot beverages and particularly for the efficient continual preparation and brewing of such beverages.
Devices of the kind involved in this case serve to prepare hot beverages such as, for example, espresso coffee fully automatically. An espresso coffee is a coffee beverage, in the preparation of which the coffee powder is subjected to a pressurized flow of brew water. For the preparation of a serving of fresh espresso coffee generic devices feature a grinder by means of which the quantity of coffee beans needed for the preparation of a serving of coffee can be freshly ground each time. The ground coffee beans are then fed in batches as coffee powder to a brewing chamber or brewing area where the coffee powder is first compacted before being subjected to a pressurized flow of brew water in a predefined quantity for extraction.
Depending on the quantity of brew water used for extraction of the coffee powder accommodated in the brewing chamber a very small to a very large beverage serving can be prepared and directed into a corresponding receptacle. The quantity of the substance—the coffee powder—used in the preparation of each beverage serving varies, if at all, only on a small scale since the volume of the brewing chamber is predefined and cannot accommodate just any large or differing quantity of substance or coffee powder, meaning, in other words, that for a so-called espresso, for the preparation of which significantly less than 100 ml water is used, practically the same quantity of coffee powder is employed as for the preparation of a so-called extended coffee, for example a milk coffee for the preparation of which it may very well be that several 100 ml of water are used. On top of this, the maximum quantity of brew water used for the preparation of a beverage is limited since from a predefined maximum quantity of substance to be brewed not just any large quantity of a high-quality tasty serving of coffee can be prepared. In the preparation of such a coffee beverage the proportion of soluble ingredients, particularly colorants, flavourings and aromatics becomes successively diminished in the coffee powder which particularly in the preparation of an espresso coffee is a drawback since the coffee beverage flowing from the beverage outlet is dark to black in color at the start of preparation whilst towards the end of preparation just a colorless liquid flows from the beverage outlet. Another drawback is that the longer the extraction duration the poorer the taste of the beverage becomes and the quantity of dissolved caffeine is increased.
Known from JP05292884A is an apparatus having an inclined screw conveyor, whereby the coffee powder is extracted in a continual counterflow. In this arrangement the water is supplied at the highest point of the conveyor before flowing through a trough in the conveyor downwards whilst the coffee powder is conveyed by the screw upwards. This apparatus as described works totally non-pressurized and roughly corresponds to the filtration of extended or American coffee. The filter time is dictated by the length of the conveyor screw and cannot be varied. In the method implemented by such an apparatus the coffee is bitter tainted and also unhealthy attendant substances such as e.g. caffeine is included in the brew to a large extent.
Described in U.S. Pat. No. 3,357,339 is an automatic coffee maker for the continual preparation of coffee. The coffee powder for extraction is held in a closed tubular tape made of a water-permeable filter material. To produce a coffee beverage the tape is continually passed through a brewing chamber where by means of a spray head located above the tape hot water is finely dispersed so that the tape including its content is wetted. The wetted tape is then passed through two extractor rolls, resulting in the essence of the coffee powder being extracted. Located below the two extractor rolls is a discharge funnel via which the coffee beverage is directed into a receptacle.
Described in WO 2005/117669 is a method and an apparatus, namely a coffee machine, for preparing a single serving of a beverage. As it reads from a first disclosed embodiment the coffee machine comprises, among other things, a bean container, below which a grinder is located, a feeder as well as a grounds carrier in the form of a circulating water-permeable conveyor belt. The grounds carrier conveys the ground coffee powder into an extraction portion in which the conveyor belt is supported by a filter plate. In the extraction portion the coffee powder is, on the one hand, compressed by means of a compression belt and, on the other hot water is supplied for the extraction of the coffee powder. In the direction of delivery the compression belt is slightly inclined to the conveyor belt, resulting in increasing compression of the coffee powder. The extracted coffee powder is transferred by means of the conveyor belt into a waste bin. The intention of this apparatus is to permit continual preparation of a coffee beverage. In an alternative example embodiment it is proposed to provide two conveyor belts for conveyance, provided with a plurality of partitions. The two conveyor belts pass between two plates in passing through the extraction portion. These partitions are intended to form chambers for receiving the aromatic—coffee powder—and for extraction thereof. In some of the further example embodiments the conveying member is configured as a screw conveyor each provided with helical flights of constant pitch. In one example to create discrete chambers for receiving the aromatic a slotted caterpillar-type track is proposed, engaging the helical flights of the screw conveyor.
In another example disclosed in this publication, a dual screw conveyor is proposed, the helical flights of which interengage to create the discrete chambers. In conclusion, screw conveyors are also proposed, the core of which changes in diameter, namely becoming flared into a compacting cone. The intention here is to diminish the screw space between the core, the helical flights and the tubular wall encasing the screw conveyor so that an aromatic conveyed by means of the screw conveyor is compacted in the direction of delivery. Where compaction occurs in the extraction portion, a seal location needs to be created to prevent the aromatic being wetted before the seal location. When compaction occurs downstream of the extraction portion the aromatic can be extracted thereby. In these examples too, the helical flights always feature a constant pitch.